Dead corals litter a beach in Bolinao, Philippines. Global warming—which causes ocean acidification and contributes to coral bleaching—is compounding the threats posed by destructive fishing techniques, coastal development, forest destruction, and aquaculture. These stresses are putting hundreds of coral and fish species and millions of people dependent on Filipino reefs at risk.1

Key Facts

The coral reefs of the Philippines—the second-largest in Southeast Asia—support hundreds of species of corals and fish.2,3,4,5 Already endangered by direct human activity, these reefs are under additional pressure from global warming.2,3,6,18

The Philippines lies within the Coral Triangle, which includes more than 75 percent of all coral species and 35 percent of the world's coral reefs.5 The region's reefs are worth more than U.S.$2 billion annually because of the fishing, tourism, and storm protection they provide.5

Some 98 percent of Philippine reefs are classified as threatened, with 70 percent at high or very high risk.2,5 Unsustainable practices such as blast fishing and cyanide fishing are thought to be the largest contributors to reef degradation.2,6

Climate change is increasing both the temperature and the acidity of the ocean. Rising temperatures increase the risk of coral bleaching. When the Philippines suffered its first mass coral bleaching at the end of the twentieth century, 80 percent of the corals around Bolinao were affected. If we continue on a path of high heat-trapping emissions, acidity levels could begin to deprive corals of the ingredients they need to build skeletons by mid-century.2,3,8,12,18

Details

The coral reefs of the Philippines are the second-largest in Southeast Asia, covering 10,000 square miles (26,000 square kilometers).5 The reefs support extraordinary biodiversity, including more than 400 species of hard coral—12 of which are unique to the area—and more than 900 species of reef fish.2,3,4

Filipino residents depend on these tremendous natural resources for fishing, tourism, and storm protection, valued at more than U.S.$2 billion annually.5

However, human activity—including fishing, coastal development, farming, and fish farming—also poses a growing threat to Philippine coral reefs.6 Environmentally destructive fishing practices are the largest contributor to reef degradation.6 Although techniques such as blast fishing and poison fishing are banned, enforcement is lacking.2 Fishers often use cyanide to stun fish, making them easier to catch. However, when used repeatedly, this technique can kill corals.2

More than 80 percent of the original tropical forests and mangroves in the Philippines have been cleared, with some converted to fish ponds.7 These changes allow more sediment and nutrients to flow onto and smother the reefs.6,7 Destruction of mangroves also leaves coastal areas vulnerable to storms, waves, and erosion.8,9,10,11 (For more information on mangroves, see hotspot on Kolkata, India.)

Nearly two-fifths of Southeast Asia's coral reefs have already been destroyed.8 Today only 10 percent of Philippine reefs are considered healthy or very healthy.5

Global Warming Worsens Existing Threats

The region's reefs cannot afford two additional major stresses posed by climate change. These include further increases in ocean temperatures, which can trigger coral bleaching, and ocean acidification, which at critical thresholds makes it difficult for corals to build shells and skeletons.8,12

Corals' spectacular coloration comes from symbiotic algae, which also nourish them.13 When rising ocean temperatures or ultraviolet light stress the corals, they lose their colorful algae, leaving only transparent tissue covering their white calcium-carbonate skeletons.14 If the stresses are sustained, the corals die.13,15 Even small increases in water temperature can cause coral bleaching.

Since 1950, global mean sea surface temperatures have risen roughly 1° F (0.6° C).16 The intensity and frequency of coral bleaching has increased significantly over the past 30 years, causing death or severe damage to one-third of the world's corals.13,17

The Philippines first suffered mass coral bleaching in 1998-99.3 Reefs off northern Luzon, west Palawan, the Visayas, and parts of Mindanao were affected. The worst bleaching—which affected 80 percent of corals—occurred around Bolinao.3,18

What the Future Holds

Continued acidification of the ocean as it absorbs our carbon emissions poses another danger to corals and other sea animals that need calcium carbonate to build shells or skeletons.13,19,20 Scientists warn of a threshold point where the ocean becomes so acidic that calcium carbonate—in the mineral form that corals use—is unavailable to corals for building reefs.13,21,19,22 Studies show that a doubling of atmospheric carbon dioxide would reduce coral calcification more than 30 percent.13,23

Loss of biodiversity in the Coral Triangle is another expected impact of global warming. As corals die off, the number of species supported by the reef declines, and local extinctions can occur.13,24